Effects of season, incubation temperature and cell age on progesterone and prostaglandin F₂α production in bovine luteal cells

Effects of season and incubation temperature on progesterone and prostaglandin F₂α (PGF₂α) production by bovine luteal cells were examined. Estrous cycles of Israeli-Holstein cows were synchronized and ovaries collected following slaughter on Day 11 of the estrous cycle in winter and summer, and on Day 16 in winter. After enzymatic dispersion, cell count and viability determination, 300 000 luteal cells were incubated at 38 or 40°C for 2 h followed by 16 h at 38°C. Effects of bovine luteinizing hormone (LH) and forskolin, with or without PGF₂α were examined. Cell number and viability were lower in summer than in winter. Incubation temperature did not affect cell viability. Winter Day 11 cells incubated at 40°C produced about 30% less progesterone than when incubated at 38°C. In summer Day 11 cells incubated at 38°C, LH or forskolin stimulated progesterone production was lower than in winter, and was not further reduced by incubation at 40°C. In winter Day 16 cells, less progesterone was produced compared with winter Day 11 cells (except for basal production after 2 h), and incubation temperature did not modify this result. Addition of PGF₂α to the medium did not affect progesterone production. PGF₂α production by luteal cells on Day 11 after 2 h incubation was higher in summer than in winter, being five and two times higher at 38°C and 40°C, respectively. These data indicate that the capacity of luteal cells to produce progesterone is impaired by both long-term seasonal heat stress and short-term incubation temperature effects.